FIR: store in ARGUMENT_TYPE_MISMATCH whether it's due to nullability

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -961,6 +961,7 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
         ArgumentTypeMismatchImpl(
             firSymbolBuilder.typeBuilder.buildKtType(firDiagnostic.a),
             firSymbolBuilder.typeBuilder.buildKtType(firDiagnostic.b),
+            firDiagnostic.c,
             firDiagnostic as FirPsiDiagnostic<*>,
             token,
         )

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -688,6 +688,7 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = ArgumentTypeMismatch::class
         abstract val expectedType: KtType
         abstract val actualType: KtType
+        abstract val isMismatchDueToNullability: Boolean
     }
 
     abstract class NullForNonnullType : KtFirDiagnostic<PsiElement>() {

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -1105,6 +1105,7 @@ internal class ConditionTypeMismatchImpl(
 internal class ArgumentTypeMismatchImpl(
     override val expectedType: KtType,
     override val actualType: KtType,
+    override val isMismatchDueToNullability: Boolean,
     firDiagnostic: FirPsiDiagnostic<*>,
     override val token: ValidityToken,
 ) : KtFirDiagnostic.ArgumentTypeMismatch(), KtAbstractFirDiagnostic<PsiElement> {